Fluorinated organic cyclic peroxides and process therefor

ABSTRACT

THE SPECIFICATION DISCLOSES HIGHLY FLUORINATED COMPOUNDS EACH CONTAINING A 3 TO 16 MEMBERED RING WHICH INCLUDES A CARBON-BONDED PEROXIDE GROUP. THESE COMPOUNDS ARE PREPARED BY FLUORINATING A COMPOUND HAVING 2 OXYGEN ATOMS BONDED TO CARBON TO EFFECT RING CLOSURE TO FORM THE PEROXIDE-CONTAINING RING. THE COMPOUNDS OF THE INVENTION ARE USEFUL AS OXIDANTS AND AS POLYMERIZATION INITIATORS.

3 632 606 FLUORINATED oRoANic CYCLIC PEROXIDES AND PROCESS rnnnnnon Richard L. Talbott and Phillip G. Thompson, White Bear Lake, Minn., assignors to Minnesota Mining and Manufactoring Company, t. Paul, Minn.

No Drawing. Continuation-impart of application Ser. No. 397,669, Sept. 14, 1964. This application May 20, 1968, Ser. No. 730,598

Int. Cl. C0711 11/00 U.S. Cl. 260338 Claims ABSTRACT OF THE DISCLOSURE The specification discloses highly fluorinated compounds each containing a 3 to 16 membered ring which includes a carbon-bonded peroxide group. These compounds are prepared by fluorinating a compound having 2 oxygen atoms bonded to carbon to effect ring closure to form the peroxide-containing ring. The compounds of the invention are useful as oxidants and as polymerization initiators.

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of our copending application Ser. No. 397,669 filed September 14, 1964 and now abandoned.

SUMMARY OF THE INVENTION This invention relates to a new class of fluorinated oxidant compounds. More particularly, it relates to new highly fluorinated cyclic peroxides and to a process for their preparation.

Generally, although they are energetic oxidants, the compounds of the invention are much more stable thermally than the corresponding hydrocarbon cyclic peroxides which may react violently under ordinary conditions. The compounds of the invention are therefore considerably more easily handled, a fact which enhances their utility greatly. In addition to their utility as oxidants, they are useful as initiators in the polymerization of ethylenically unsaturated monomers.

It is an object of the present invention to provide a new class of fluorinated oxidant compounds. It is another object of the invention to provide highly fluorinated organic cyclic peroxides. It is another object of the invention to provide a process for the production of highly fluorinated cyclic peroxides. Other objects of the invention will become apparent from reading the following disclosure.

The compounds of the invention include gases, oily or waxy materials and solids, depending in large measure upon their molecular weights. They are highly fluorinated organic cyclic peroxides having a 3 to 16 membered ring containing carbon and one or two peroxy groups, said ring having substituents which are electronegative and non-reducing with respect to the peroxide group and which have Hammett meta substituent constants greater than +0.3, said substituents including bridging atoms (in some of the compounds). The Hammett constants are defined in the article by H. H. Jaffe, Chemical Reviews, vol. 53, pages 191-261. (1953). Such groups include NF =NF, N0 ONF F, Cl, Br, highly fluorinated organic groups, particularly perfluorinated organic groups (especially perfluoroalkyl radicals) partially fluorinated perhalogenated organic groups (e.g. CF Cl) etc. Some of these (NF =NF, N0 and ONF are oxidizing groups which contribute significant additional oxidizing power to the compounds. The compounds of the invention include the perfluorocarbon cyclic peroxides, i.e. those which contain only carbon and fluorine in addition to the cyclic peroxide group or groups, as well as those which contain only oxidizing groups (such as those just mentioned) in addition to carbon, fluorine and the cyclic peroxide groups. The peroxide-containing ring can also include hetero atoms, such as oxygen, nitrogen and sulfur. Preferably, the compounds of the invention contain not more than 18 carbon atoms.

Fully equivalent with the perfluoroalkyl radicals for purposes of the present invention are perfluoroalkyl radicals containing perfluorinated carbocyclic and heterocyclic rings, for example, perfluoropiperidyl, as well as perfluorocyclohexyl, perfluorocyclohexylethyl and the like radicals. As used herein, the term perfluorocarbon cyclic peroxide includes compounds containing such groups. Likewise, the perfluoroalkyl radicals can be substituted with certain electronegative groups which may replace one or more fluorine atoms or CE; groups.

Broadly speaking, the process of the invention consists in direct fluorination of compounds having a molecular structure in which at least two oxygen atoms are directly bonded to carbon, e.g. in carbonyl, carboxyl, ester, orthoester, carbinol, ether, and the like groups.

Ring closure to form the highly fluorinated cyclic peroxides can be accomplished by formation of a bond between two oxygen atoms. The fluorination apparently provides conditions which are conducive to the ring closure. The two oxygen atoms may be carried by different carbon atoms in the precursor. If two oxygen atoms are bonded to the same carbon atom in the precursor structure, a three membered peroxy-containing ring can be formed. Alternatively, if two such groups are involved in the ring formation the resulting ring can contain two peroxide groups. Coupling, combination, modification, cleavage and fluorination of carbon chains, e.g. side chains, may occur in the proces. In certain cases carbon chains longer than those of the starting materials are produced. Table I (in which R and R represent structural portions of the starting material, R and R% represent corresponding highly fluorinated structural portions of the compounds of the invention, M represents a metal ion and n represents the valence of M) illustrates several general types of these reactions.

Highly fluorinated linear polymers With repeating units :ontaining rings which include carbon-bonded peroxide groups can result from the fluorination of polymeric :helates according to the process of the invention and )olymers containing cyclic diperoxides can be produced 'rom the fiuorination of dicarboxylic acid salts in the .ame way. Although monoand di-peroxides are the major cyclic peroxides isolated in the examples, fluorine- :ontaining cyclic triperoxides can also be formed by procasses described herein.

The process of the invention involves treating an oxygen-containing reactant compound as described herein vith elemental fluorine at a temperature in the range of rom about 100 C. to about +50 C. The apparatus 1Sd is preferably constructed from Monel metal or copper. Solid, liquid or gaseous starting materials can be used. Where the reactants contain phenolic, enolic, acidic or other salt-forming oxygen groups, it is preferred to use the corresponding metal salts as starting materials for the direct fiuorination. For this purpose, alkali metals, alkaline earth metals, transition metals such as nickel and the like can be used. Salts (or metal chelates) are conveniently used when carboxylic acids are employed as starting materials and beta-diketones are conveniently used in the form of the metal chelates. Negatively substituted 1,3-dioxanes, however, can be easily used as such.

Illustrative of the starting materials useful in the present process are chelates of acetylacetone derivatives, such as 3-bromoacetylacetone, hexafiuoroacetylacetone, etc.; chelates of perfluorobiacetyl hydrate U. Org. Chem. 30, 2472 (1965)]; salts of fluorocarbon acids such as perfiuorohexanoic acid, perliuorodecanoic acid, chlorodifluoroacetic acid, and nitrodifluoroacetic acid,

HOOCCF(CF3)O(CF2)3OCF(CF3)COOH, HOOCCF(CF3)O(CF2)5OCF(CF3)COOH (US. Pat. 3,250,807),

Where r is l to 3 (US. Pat. 3,250,806); tetrahydroperfluoroalkanediols such as 2,2-difluoropropane-1,3-diol and 1,l,5,itetrahydroperfluoropentane-1,S-diol; monoand dipotassium salts of nitromalonic acid; 2-chloro-2,3,3-trifiuorobutane 1,4 diol; 1,2-bis(difiuoroamino)ethylene glycol; disodium salt of omega, omega, omega-trifluoroacetoacetic acid; and the like. Table II exemplifies a number of compounds which are suitable starting materials for the process as Well as the products of the invention produced from them.

TABLE II-Continued Product Reactant H \I NaOCOFzCONa Where two oxygen atoms are attached to the same car- :on atom, as in carboxylic acid salts, mixtures of mono- )eroxide and diperoxide compounds may result.

Inert gases, liquids and solids can be used as diluents or the organic oxygen-containing reactants. The finely livided reactant can be suspended in a liquid or a solid nert diluent. Sodium fluoride is an example of such a olid diluent. Among the fluorine-inert liquids which can ae used as diluents in the process of the invention are perluorinated hydrocarbons, e.g. perfluorooctanes, perfluoohexanes, and the like; perfluorocyclohexane; perfluorilated cyclic ethers such as perfluorobutylfuran; perfluoinated tertiary amines such as tris-perfluoro-n-butylamine; .nd the like. Commercially obtainable fluorocarbons may :ontain an amount of material which is not inert toward luorine, and in such cases, fluorine gas is passed through he selected fluorocarbon for a time in small amounts just uflicient to render it substantially completely inert toward luorine. When an inert liquid diluent is employed in the rocess of the invention, the hyperfluorinated reaction )lOdllCt generally dissolves in the diluent.

The fluorine and other gases used are conveniently inroduced under slight positive pressure. Preferably, the luorine is diluted with nitrogen or other inert gases such is argon or helium, or a Freon, such as dichlorodifluoomethane or the like to give fluorine concentrations upvards of about 0.1 percent. Undiluted fluorine in the gas tream, can in many cases be used, although great caution .nd slow addition are required.

The reactant is placed in a suitable container with dilu- :nts or suspending media if desired, and is then contacted vith fluorine for a period ranging from about 10 minutes about 6 to 12 hours and upward, depending on the .mount of starting material charged and the ease with vhich the fluorination is accomplished. Generally speakng, once the process has gone to completion, no further luorine reacts so that when the products are volatile and hus are swept into the traps, continuation of the flow of luorine is not deleterious. In the case of non-volatile olid or non-volatile liquid products, however, excessive xposure to fluorine should be avoided to eliminate the )ossibility that degradative reactions may occur. Residual luorine should be flushed out of the reactants and the .pparatus with dry nitrogen or the like after completion if the reaction to avoid unpleasant and toxic exposure 0 fluorine as well as untoward effects owing to the strong ixidizing power of this substance.

The desired products are ordinarily isolated from the eaction mixture by fractional condensation employing raps cooled with Dry Ice, liquid air, ice-salt mixtures and he like where the products are low-boiling, and other tppropriate temperature controls where high boiling liqtids or solids are produced. Where the products are colacted in solvents, any insoluble material is removed by iltration and the product is recovered by evaporation of he solvent, preferably under reduced pressure. Fraction- LtiOl'l may be necessary if separation of the product is lesired although for some purposes, the reaction product nixture can be used as such. Ultimate separation of the roducts of the invention is conveniently accomplished y chromatographic techniques in small scale runs; in arger runs, other known methods of fractionation such is fractional distillation can be used. In the chromatographic separation of the products, the temperature is naintained at the minimum temperature at which conenient retention times are obtained. Alternative separaion and purification can be accomplished by the usual neans, taking into consideration the strongly oxidizing .ature of the products, and maintaining temperatures at minimum.

Crude or impure products of the invention are preferbly stored well below room temperature, conveniently sing solid carbon dioxide or liquid nitrogen as coolants.

The compounds of the invention are useful as oxidants, or example for bleaching and the like and for oxidizing agents in chemical synthesis. They are especially useful in areas where fluorinated chains confer advantages owing to their special properties of solubility in fluorinated solvents and reduced solubility in other solvent systems. Also, as noted previously, they can be used as initiators in the polymerization of ethylenically unsaturated compounds.

The following specific examples illustrate the process and products of the invention. All parts are by weight in the examples unless otherwise specified.

EXAMPLE 1 The copper chelate of hexafluoroacetylacetone o GE -g (I-C F3 W CH is prepared as described in the literature (A. L. Henne, M. S. Newman, L. L. Quill, and R. A. Staniforth, I. Am. Chem. Soc., 69, 1819 (1947)), M.P. 113-115 C., and is subjected to fluorination as follows:

The fluorination of the copper chelate of hexafluoroacetylacetone is carried out using a static bed procedure in a 450 cc. copper vessel of cylindrical shape, equipped with a gas inlet tube, a gas outlet tube, and a polychlorotrifluoroethylene rupture disk. A 1.6 g. sample of the copper chelate of hexafluoroacetylacetone (about 6.7 milliequivalents of hexafluoroacetylacetone) is placed in a copper tray in the copper fluorinating vessel. The reactor is immersed in a cooling bath at about 20 C. and flushed for 45 minutes with a stream of dry pre-purified nitrogen to displace air. Fluorine (commercially available, pure) is introduced into the nitrogen stream (using monel metal fittings). The fluorine-nitrogen mixture is passed into the vessel and the volatile, entrained products formed are recovered from the eflluent stream, which is passed through an iron tube containing granular sodium fluoride at room temperature to remove hydrogen fluoride (which is present in commercial fluorine and also is formed in the reaction) and then through a trap 1mmersed in liquid air. A stream of about 3% (by volume) fluorine in nitrogen is passed through the reactor at a flow rate of about 0.016 cubic foot per minute for three hours (a total of 0.07 mole of fluorine). I

The desired product is formed rapidly during the initial period of fluorine delivery and is produced more slowly during the later stages of the fluorlnatron. The fluorine fiow is then discontinued and the cooling bath removed; the reaction vessel is thereafter purged with nitrogen for one hour.

If the solid residues are then removed from the reactor, ground into fine powder, and returned to the reactor, further production of the desired material is achieved by repeating the fluorination procedure.

The contents of the liquid air trap are maintained at liquid air temperature until they are worked up as follows: The non-condensable gases are removed from the trap at liquid air temperature under reduced pressure, and the condensate is then allowed to warm slowly while it is fractionated at about 0.1 mm. pressure through the traps designated A, B and C. Trap A is cooled in a solid carbon dioxide-trichloroethylene bath at about 78 C., trap B in a bath of trichlorofluoromethane slush at about 111 C., and trap C in a bath of liquid nitrogen at about 196 C. Trap A is found to contain about 0.38 millimole of product, which is chiefly a mixture of cisand transperfiuoro 3,5 dimethyl-1,2- dioxolane. Trap B is found to contain a small amount of this compound along with other products. Cisand trans-perfluoro-3,5dimethyl-1,2-dioxolane is isolated in pure form from the product mixture by means of vapor Phase romat graphy. For this process a column 2 meters in length and /2 inch in diameter packed with silicone gum rubber (commercially available as SEF3O', from General Electric C0., Inc.) (20%) coated on 3060 mesh acid-washed filter aid (diatomaceous earth) (80%) and maintained at about 25 C. is used. An 8-volt thermistor is used as a detector. Helium is employed as a carrier gas at a flow rate of about 200 mL/min. Cisand transperfluoro-3,5 dimethyl 1,2 dioxolane are thus obtained. The yield of pure material thus obtained is about of theoretical based on the amount of hexafluoroacetylacetone employed as the copper che'late. The cisisomer is obtained in greater amount.

The structures of the products are as follows:

dimethyl-1,2-dioxolane Cis-perfluoro 3,5 dimethyl 1,2-dioxolane is a clear, colorless liquid at room temperature. llts F nuclear magnetic resonance spectrum contains absorptions at 75.7 (assigned to the CF groups), at l28.5 (assigned to the CF group), and at 110 5 and 126 5 as an AB pattern (assigned to the rnagnetically-non-equivalent fluorines of the CF group). All the absorptions are complex multiplets. The infrared spectrum of this material shows a strong absorption at 11.6 microns.

Trans-perfluoro-3,5 dimethyl 1,2-dioxolane is also a clear, colorless liquid at room temperature. Its F nuclear magnetic resonance spectrum contains absorptions at 76.74) (assigned to the CF groups), at 114 5 (assigned to the CF group), and at 132.5 (assigned to the CF group). All the absorptions are complex multiplets. In the trans-isomer the fluorines of the CF group are magnetically equivalent. The infrared spectrum of this material shows a medium intensity absorption at 11.45 microns. The infrared spectra of both isomers show strong absorptions in the region 7.5 to 9.5 microns.

Both isomers of perfluoro-3,5-dimethyl-1,2-dioxolane are immiscible with water and may be washed with water for periods up to 1 hour with no evidence for hydrolysis. Both isomers are recovered unchanged after exposure to mercury for thirty minutes. The trans-isomer is stable at room temperature for several months.

Analytical data on a sample of chromatographed cisand trans-perfluoro-3,5 dimethyl 1,2-dioxolane were as follows:

Calculated for C F O (percent): C, 21.4; F, 67.4. Found (percent): C, 21.4; F, 66.8.

A molecular weight determination for this material gave a value of 275; the calculated value is 282. The sample was found to havean oxidizing power of 6.8 milliequivalents of iodine per gram of sample (calculated for a two-electron change, 7.1). The mass cracking pattern of a sample of chromatographed cisand transperfluoro 13,5 dimethyl 1,2 dioxolane shows peaks at m/e=69 (assigned to C1 47 (assigned to CFO), 97 (assigned to CF CO), and 263 (assigned to the parent molecule minus one fluorine atom) in addition to many other peaks consistent with the structure.

EXAMPLE 2 Z-hydroxy i2 trichloromethyl-1,3-dioxane is prepared by the dropwise addition of trichloroacetyl chloride to a stirred suspension of 1,3-propanediol in dry ether, as described by Hibbert and Greig, Can. J. Res., 4, 254 (1931). The residual liquid remaining after ether and hydrogen chloride are removed by evaporation under vacuum is used directly in the fluorination reaction.

The fluorination reaction is carried out in a brass rectangularly-shaped box reactor having a sintered Monel plate suspended across it. The vessel is equipped with a gas inlet tube below the sintered plate and a gas outlet tube and brass blow-out cap above it. A 2.0 g. sample of Z-hydroxy 2 trichloromethyl-1,3-dioxane is spread out on the sintered plate in the fluorinated vessel. The reaction is carried out over a 4-day period. On the first day, the reactor is immersed in a cooling bath at about 70 C., flushed with nitrogen, fluorine is introduced into the nitrogen stream, and the mixture is passed into the vessel. The efliuent stream is passed through an iron tube containing sodium fluoride at room temperature to remove hydrogen fluoride and then through a trap immersed in liquid air to recover the volatile, entrained products. A stream of 3% (by volume) of fluorine in nitrogen is passed through the reactor at a flow rate of .02 cubic ft./ min. for 7 hours. After 4 hours the temperature of the bath is raised to about -50 C. and the process continued at that temperature for the remainder of the 7-hour period. The reactor is purged with nitrogen for 1 hour, while being allowed to warm to room temperature, and the trap containing the volatile products is removed. The reactor is capped and allowed to stand overnight. On the second day, a new trap is connected to the exit line beyond the sodium fluoride scrubber. The reactor is immersed in a cooling bath at about 50 C. and a stream of 7% (by volume) fluorine in nitrogen is passed through the reactor at a rate of about .007 cubic ft./min. for 2 hours. For the following 5 hours, a concentration of 20% and a flow rate of about .008 cubic ft./min. are maintained. After 2 hours at this concentration the temperature of the cooling bath is raised to 20 C. and the process is continued to that temperature for the remainder of the 7-hour period. The reactor is purged with nitrogen for 1 hour, while being allowed to warm to room temperature, and the trap containing the volatile products is then removed. The reactor is capped and allowed to stand at room temperature overnight. On the third day, a new trap is connected to the exit line immediately following the sodium fluoride scrubber. The reactor is immersed in a cooling bath at about 0 C. and a stream of about 11% (by volume) fluorine in nitrogen is passed through the reactor at a rate of about .02 cubic ft./min. for 2 hours. For the next 5 hours a concentration of about 20% and a flow rate of about .008 cubic ft./min. are maintained. After 3 hours the cooling bath is removed and the reaction vessel is allowed to warm to room temperature (about 20 C.); the fluorination is continued during the warming and for the remainder of the 5-hour period. The reactor is purged with nitrogen for 1 hour, after which the trap containing the volatile products is removed. The reactor is capped and allowed to stand overnight. On the fourth day, a new trap is connected to the exit line beyond the sodium fluoride scrubber. A stream of 24% (by volume) fluorine in nitrogen is passed through the reactor at a rate of about .02 cubic ft./min. for 1 hour. For the next 6 hours a concentration of about 36% (by volume) fluorine in nitrogen and a flow rate of .01 cubic ft./min. are maintained. After 1 hour at this concentration the temperature is raised to about 38 C. and maintained there for the remainder of the 6-hour period. The reactor is purged with nitrogen for 1 hour, while it is allowed to cool to room temperature. A total of 2.50 moles of fluorine is introduced into the reactor during the 4-day period.

Only a very small quantity of volatile products is formed on the first and second days. A somewhat larger quantity is obtained on the third day, but the major proportion of the products is obtained on the fourth day. The crude products are stored well below room temperature. The products of the fourth day are removed under reduced pressure from the trap which was at liquid air temperature, and fractionated at about 1 mm. pressure through the traps A (78 C.), B (11l C.), and C (l96 C.), successively. Trap A is found to contain more than 1.8 millimoles of products, which include hexafluoro-1,2-dioxolane 2,2,2-trichloro 1,1 difluoroethyl oxyfluoride, 2,2-dichloro-l,l,2-trifluoroethyl oxyfluoride, 1,3-bis(fluoroxy)hexafluoropropane, and 3-fluoroxytetrafluoropropionyl fluoride. Trap B is found to contain about ).8 'm-illimole of products, including hexa'fluoro-l,2-dioxoabout 4.8 millimolesi of products, including carbon dioxide, carbonyl fluoride, and pentafluoroethyl oxyflu-oride.

The pure oxyfluorides are isolated from these mixtures by vapor phase chromatography.

Pure hexafluoro-1,2-dioxolane is isolated from these nixtures by first washing' the mixtures with water and :henvaporphase chromatography of the resulting mix- :ures. A column of perfluorotributylarnine coated on acid washed Celite operated at C. is used.

'An'alysis.'Calcd for C F O (percent): C, 19.7; F, I 52.8. Found (percent): C, 19.9; F, 62.5.

Ihe F nuclear magnetic resonance spectrum of hexav iuoro- 1,2-dioxolane shows an absorption at +125.0

(fivefold) for the center'CF group and anabsorption at =+96.6 (triplet) for the CF groups adjacent to the peroxide group'The coupling constant:is3.3 :c=./s. I I z EXAMPLE 3 1 The fiuorination of the nickel chelate of h'ex afluorm gen stream, andthe mixtureis passed into the vessel. The

effluent stream is passed through an irontube containing sodium fluoride atroom temperature to remove any hydrogen fluorideand then through a trap immersed in liquid air. A stream of about 4% (by volume) of fluorine in nitrogen is passed through the reactor at a flow rate of: 001 cubic ft./-min. for .15 minutes, then a 20% stream at, a flow rate of .007 cubic ft./min.'for ,1 hour, and finally a 34% stream at a flow rate of 0O4,cubic,ft./min. for 2 hours. During this 3 /2 hour reaction period a total of 0.30 mole of fluorine is introduced into the reactor; the 2 7 temperature inside the reactor varies from,1722 C.

' The fluorine flow is. discontinued and the reaction vessel is then purged with'nitrogen for hour. The residual mae terial in the reactor is found to weigh, about 0.6 g; it consists principally of NaHF and NaF.

The non-condensable gases are removed from the trap at liquid nitrogen temperature under reduced pressure.

lcetylacetone is carried out using a static .bed procedure lcetone) is placed in a copper tray in the copper fluori- 'nating-vessel=..The reactor is immersed in a cooling bath it about -20 C. and flushed for one hour with a strearn= )f dry prepurified nitrogen to displaceair. Fluorine (com nerically' available, 95% pure) is introduced into the I nitrogen stream (using Monel metal fittings). The=fluorine-. t

iitrogen mixture is passed into the vessel and the volatile,

' :ntrained products formed are recovered from the efliuent dream, which is passed through an iron tube containing 7 The-liquid air trap is found to contain 9.3 millimoles of condensed products, including the two isomers, cisand trans-perfluoro-3',6-dimethyl-s-tetroxane. This material is isolated in pure form from the mixture by means of gas chromatography. For this process a column 8-7'in length and /2" in diameter packed with perfiuorotributylamine (33%) coated on -60 mesh acid-washed filter aid'(di-.

atomaceous earth) (67%) and maintained at'about 0 C. is used. An. 8-volt thermistor is used as the detector. Heliz um is employed as. the carrier gas at a flow rate of 130 granular sodium'fluoride at roorn temperature to'remove iydrogen fluoride (which is present in commercial fluorine and also is formed in the reaction) and then through a ;rap immersed in liquid air. A stream of about 2.3% (by lolume) fluorine in nitrogen is passed through the reactor it a flow rate of about 0.02 cubic feet per minute for siX room (a total of 0.15 mole of fluorine). The desired iroduct is formed rapidly during the initial period of luorine delivery and is produced more slowly during the ater stages of the fluorination. The fluorine flow is then liscontinued and the cooling bath removed; the reaction lessel is thereafter purged with nitrogen for one hour.

The contents of the liquid air trap are maintained at iquid air temperature until they are worked up as folows: the non-condensable gases are removed from the rep at liquid air temperature under reduced pressure, and :he condensate is then allowed to warm slowly while it is fractionated at about 0.1 mm. pressure through the traps iesignated A and B. Trap A is cooled in a solid carbon lioxide-trichloroethylene bath at about 78 C., and trap 3 is cooled in a bath of liquid nitrogen at about -196 C. ['rap A is found to contain about 0.28 millimole of prodlot, which is chiefly cisand trans-perfluoro-3,S-dimethyll,2-dioxolane. This material is isolated in pure form by :hromatography by the procedure set forth in Example 1.

EXAMPLE 4 The sodium salt of trifluoroacetic acid is fluorinated )y the static bed procedure in a brass rectangular shaped aox reactor having a sintered Monel plate suspended ICI'OSS it. The vessel is equipped with a gas inlet tube aelow the sintered plate and a gas outlet tube and brass )low-out cap above it. A 2.1 g. sample of sodium triiuoroacetate (about 15.6 millimoles) is spread out on the iintered plate in the fluorinating vessel. The reactor is iushed with nitrogen, fluorine is introduced into the nitroml./ min. The pure products are obtainediby passing the stream from the chromatographexit through cooled traps as therespective components elute. The components elut- .ing with a retention time of approximately 580 relative to CFCl under identical chromatography conditions are t the isomers, cis-perfluoro6,6-dimethyl-s-tetroxane and Using a column 12' in length and A7 in diameter packed-in the same manner as the column described in the previous paragraph maintainedat about: 23" C. at a flow. rate of about ml./rnin. with helium as the carrier gas,

the isomers cisand trans-perfluoro-3,6-dimethyl-sdetroxane elute at a retention time of approximately .544 relative to. CFCI I I The F nuclear magnetic resonance spectrum of the isolated gas chromatography fraction indicates that the relative abundance of the two isomers is approximately 1:3. The isomer present in the greater amount is considered to be the transisomer. Its spectrum contains two peaks, one at 82.4 5 due to the CF group and one at 107.1 due to the CF group. The F nuclear magnetic resonance spectrum of the cis-isomer has corresponding peaks at 82.1 and 106.9 5.

The infrared spectrum of the mixture of isomers shows the following absorptions: 7.37(m.), 8.08(s.), 8.25(s.), 8.55(m.), 8.73 (m.), 9.23(m.), 9.40(s.), 11.84(w.), 13.3(w.) and 13.68(w.) microns.

The mass spectrum is in good agreement with the assigned structure, the molecular weight is found to be 263.7 (theoretical 264.0) and the elemental analyses are as follows:

Calcd for C F O (percent): C, 18.18; F, 57.58. Found (percent): C, 17.7; F, 57.0.

EXAMPLE 5 The copper chelate of 3-nitroacetylacetone is prepared from acetylacetone, copper (II) nitrate trihydrate, and acetic anhydride according to the procedure described in the literature (J. P. Collman, R. L. Marshall, W. L. Young III, and S. D. Goldby, Inorg. Chem. 1, 704 (1962) The fiuorination of the copper chelate of 3-nitroacetylacetone is carried out using a static bed procedure in a 450 cc. copper vessel as described in Example 1. A 1.5 g. sample of the chelate is placed on a copper tray in the copper fluorinating vessel. The vessel is immersed in a cooling bath at about 20 C. and flushed for minutes with a stream of dry prepurified nitrogen to displace air. Fluorine is introduced into the nitrogen stream, and

the fluorine-nitrogen mixture is passed into the vessel. The volatile, entrained products formed are recovered from the efliuent stream, which is passed through an iron tube containing granular sodium fluoride at room temperature to remove hydrogen fluoride (Which is present in commercial fluorine and also is formed in the reaction) and then through a trap immersed in liquid air. A stream of about 3% (by volume) fluorine in nitrogen is passed through the reactor at a flow rate of about 0.016 cubic foot per minute for six hours (a total of 0.15 mole of fluorine). The fluorine flow is then discontinued and the cooling bath removed; the reaction vessel is thereafter purged with nitrogen for one hour.

The contents of the liquid air trap are maintained at liquid air temperature until they are worked up as follows: the non-condensable gases are removed from the trap at liquid air temperature under reduced pressure, and the condensate is then allowed to warm slowly while it is fractionated at about 0.1 mm. pressure through the traps designated A and B. Trap A is cooled in a solid carbon dioxide-trichloroethylene bath at about -78 C., and Trap B is cooled in a bath of liquid nitrogen at about 196 C.

Trap A is found to contain the product, 4-nitroperfluore-3,S-dimethyl-1,2-dioxolane, which is present as a mixture of isomers. The product may be purified by vapor phase chromatography by the procedure given in Example 1.

Thus is obtained 4-nitroperfluoro-3,S-dimethyl-1,2-dioxolane, which has the following structure:

l N O This compound is identified by its infrared and nuclear magnetic resonance spectra. 4-nitroperfiuoro-3,S-dimethyl-l,2-dioxolane is an oxidizing agent. It readily liberates iodine from solutions of potassium iodide and oxidizes ferrocene suspended in fiuoroinated solvents.

EXAMPLE 6 The copper chelate of 3-chloroacetylacetone is prepared by chlorination of the corresponding chelate of acetylacetone with N-chlorosuccinimide according to the procedure described in the literature (J. P. Collman, R. A. Moss, H. Maltx, and C. C. Heindel, I. Am. Chem. Soc., 83, 531 (1961)).

The fluorination of the copper chelate of 3-chloroacetylacetone is carried out using a static bed procedure in a 450 cc. copper vessel as described in Example 1. A 1.5 g. sample of the chelate is placed on a copper tray in the copper fluorinating vessel. The vessel is immersed in a cooling bath at about 20 C. and flushed for 45 minutes with a stream of dry, prepurified nitrogen to displace air. Fluorine is then introduced into the fluorine stream, and the fluorine-nitrogen is passed into the vessel. The volatile, entrained products formed are recovered from the effiuent stream, which is passed through an iron tube containing granular sodium fluoride at room temperature to remove hydrogen fluoride (which is present in commercial fluorine and also is formed in the reaction) and then through a trap immersed in liquid air. A stream of about 3% (by volume) fluorine in nitrogen is passed through the reactor at a flow rate of about 0.016 cubic foot per minute for six hours (a total of 0.15 mole of fluorine). The fluorine flow is then discontinued and the cooling bath removed; the reaction vessel is thereafter purged with nitrogen for one hour.

The contents of the liquid air trap are maintained at liquid air temperature until they are worked up as follows: the non-condensable gases are removed from the trap at liquid air temperature under reduced pressure, and the condensate is then allowed to warm slowly while it is fractionated at about 0.1 mm. pressure through the 14 traps designated A and B. Trap A is cooled in a solid carbon dioxide-trichloroethylene bath at about 78 C., and trap B is cooled in a bath of liquid nitrogen at about 196 C.

Trap A is found to contain the product, 4-chloro-perfluoro-3,5-dimethyl-1,2-dioxolane, which is present as a mixture of isomers. The product may be purified by vapor phase chromatography by the procedure given in Example 1.

Thus is obtained 4-chloro-perfluoro-3,S-dimethyl-1,2- dioxolane, which has the following structure.

The compound is identified by its infrared and nuclear magnetic resonance spectra. The compound is an oxidizing agent. It readily liberates iodine from solutions of potassium iodide and oxidizes ferrocene suspended in fluorinated solvents.

EXAMPLE 7 The copper chelate of 5,5-dihydroperfluoropentadecane- 4,6-dione is prepared from methyl perfluoro-n-decanoate and methyl perfluoro-n-propyl ketone according to the procedure described in the literature for the preparation of the copper chelate of hexafluoroacetylacetone (see Example 1).

The fluorination of the copper chelate of 5,5-dihydroperfluoropentadecane-4,6-dione is carried out using a static bed procedure in a 450 cc. copper vessel as described in Example 1. A 1.5 g. sample of the starting material is placed in a copper tray in the copper fluorinating vessel. The vessel is immersed in a cooling bath at about 20 C. and flushed for 45 minutes with a stream of dry prepurified nitrogen to displace air. Fluorine is introduced into the nitrogen stream and the fluorine-nitrogen mixture is passed into the vessel. A stream of about 3% (by volume) fluorine in nitrogen is passed through the reactor at a flow rate of about 0.016 cubic foot per minute for three hours (a total of 0.07 mole of fluorine). A longer reaction time may be used if desired. The fluorine flow is then discontinued and the cooling bath removed; the reaction vessel is thereafter purged with nitrogen for one hour.

The contents of the reactor are then extracted with a suitable solvent and the product is recovered by removal of the solvent from the extract at room temperature or below. Thus is obtained perfluoro-3-n-nonyl-5-n-propyl- 1,2-dioxolane, which has the following structure.

ornormor orwnnzom This compound may exist in both cisand trans-isomeric forms. The compound is identified by its infrared and fluorine nuclear magnetic resonance spectra. Further purification is accomplished by liquid column chromatography. Care must be taken during this procedure to avoid exposing the compound to temperatures higher than room temperature for extended periods of time. The peroxide is soluble in fluorinated solvents and insoluble in water; hence extraction procedures may be used in the purification steps.

Perfluoro-3-n-nonyl-S-n-propyl-1,2-dioxolane is an oxidizing agent. It readily liberates iodine from solutions of potassium iodide and oxidizes ferrocene suspended in fluorinated solvents.

EXAMPLE 8 The sodium salt of chlorodifluoroacetic acid (sodium chlorodifluoroacetate, ClCF CO Na) is fluorinated by the static bed procedure in a 1550 cc. cylindrical copper vessel, equipped with a gas inlet tube, a gas outlet tube, and a ead rupture disk. A 1.9 g. sample of sodium chlorodiiuoroacetate (about 12.5 millimoles) is placed in a cop- )er tray in the fluorinating vessel. The reactor is flushed vith a stream of nitrogen, and fluorine is introduced into he nitrogen stream. The volatile reaction products are aassed through an iron tube containing sodium fluoride ll. room temperature and then through a trap immersed n liquid air. A stream of about (by volume) of fluoine in nitrogen is passed through the reactor at a flow 'ate of .02 cubic ft./min. for 30 minutes and then a :tream at a flow rate of .007 cubic ft./min. for 5 hours. During this 5 /2 hour reaction period a total of 0.27 mole )f fluorine is introduced into the reactor; the temperature nside the reactor varies from 19 C. The fluorine flow s discontinued and the reaction vessel is then purged with iitrogen for /2 hour. The residual material in the reactor s found to weigh about 0.6 g.; it consists principally of IaHF and NaF.

The contents of the liquid air trap are worked up as ollows: The non-condensable gases are removed from he trap at liquid nitrogen temperature under reduced aressure, and the condensate is then allowed to warm :lowly while it is fractionated at about 0.1 mm. pressure hrough traps designated A and B. Trap A is cooled in ;olid carbon dioxide-trichloroethylene ('-78 C.) and .rap B is in liquid nitrogen (196 C.). Trap A is ound to contain liquid products including 3,6-difluoro- S,6-bis (chlorodifluoromethyl -s-tetroxane. Identification s made from infrared and F nuclear magnetic resoiance spectra.

EXAMPLE 9 The dilithium salt of hexafluoro-2,2-propanediol is preaared and the compound irepared from it as follows:

A solution of 28.4 grams of hexafluoro-2,2-propanediol n 100 milliliters of water is carefully titrated to pH 8.0 vith aqueous normal lithium hydroxide solution. Most )f the Water is then removed in a stream of dry air at 'oom temperature, and the resulting syrupy mass is dried n a vacuum desiccator. A solid white residue remains 29.50 grams, about 90 percent of theoretical yield) and s identified as the hydrated monolithium salt of hexaluoro-2,2-propanediol by its infrared and F N.M.R. pectra.

Analysis.Calcd for C HF O Li-LSH O (percent): 3, 16.4; H, 1.8; F, 52.2. Found (percent): C, 16.8; H, ..7; F, 52.4.

The hydrated monolithium salt of hexafluoro-2,2-pro- )anediol (29.5 grams) is heated under high vacuum at .00 C. and the volatile products are condensed into a rap which is then cooled to l96 C. The volatile prodtcts are identified as hexafluoro-2,2-propanediol, water Ll'ld hexafiuoroacetone by their characteristic infrared pectra. A solid residue remains (13.9 grams, about 94 )ercent of theoretical yield) and is identified as the aniydrous dilithium salt of hexafluoro-Z,2-propanediol by ts infrared and F N.M.R. spectra.

Analysis.Calcd for C F O Li (percent): C, 18.3; 58.2; Li, 7.2. Found (percent): C, 18.2; F, 55.2; Li, '01.

This compound decomposed rapidly at 150 C.

A 0.418 g. (2.14 mmole) sample of dry (CF C(OLi) fluorinated using the following conditions: 7.5% F (N liluent) at 100 cc./min. for 30 minutes followed by 15% at 75 cc./min. for 2% hours. Total F passed through he reactor is approximately mmoles. The residue (as letermined by IR and powder X-ray spectroscopy) is argely LiF together with small Li SiF and probably ome CF CO Li and a trace of unidentified material.

The volatile products are fractionated through traps cooled to -78 119 and 196. The l96 fraction (2.96 mmoles) and -119 fraction (0.92 mmole) are subjected to gas chromatography to separate the various products therein. This is performed using a 3 m. (nC F N column at 30 C. with a flow rate of 150 cc./min. The component eluting at 22.7 min. is examined carefully using various techniques and found to be The yield of this compound (based on mmoles of starting material used, mmoles of product obtained and GLC area ratios) is 53% of theory. Since the compound is explosive and unstable, it is likely that an even higher yield is originally formed in the reaction.

The F N.M.R. spectrum of (OF CO shows only one absorption, a strong singlet at 76.84) and its infrared spectrum shows the following absorptions: 7.39(s.), 7.84(s.), 8.l0(s.), 825 (shoulder), 9.00(W.), 9.78(w.), 10.25(s.), and 14.01(m.) microns.

This new compound has a pale yellow color in its liquid or solid states. Absorption spectroscopy in the visible and ultraviolet region (8000 A. to 2100 A.) of (CF CO in the gas phase shows a broad, moderately weak absorption band (x =306 III/L) extending very weakly into the violet and blue part of the visible spectrum. This suggests a very pale yellow color for gaseous (CF CO as well. Below 220 mg, a second absorption band of (CF CO begins to rise sharply. The mass spectrum and molecular weight of (CF CO also are consistent with the assigned structure. The empirical formula is also established as C F O by elemental analysis.

Calcd for (1 1 0 (percent): C, 19.78; F, 62.64. Found (percent): C, 20.0; F, 63.3.

The gas chromatography retention time of (OF CO relative to CFCl is 82. Under identical conditions, the retention time of (CF CO relative to CFCl is 30.

The fiuorination of the monolithium salt of hexafluoro- 2,2-propanediol (see above) (I. Am. Chem. Soc. 89, 2263 (1967)) also yields perfluorodimethyldioxirane. The fluorination conditions are similar to those described above.

EXAMPLE 10 The dilithium salt of chloropentafluoro-Z,2-propanediol is prepared and the compound is prepared from it as follows:

In the manner described in Example 9, chloropentafluoro 2,2-propanediol is converted into the hydrated monolithium salt, and subsequently the anhydrous dilithium salt is recovered. This compound decomposes rapidly at 115 C.

-A 0.299 g. sample of dried CF Cl(CF )C(OLi) is fluorinated at room temperature using the following concentrations and flow-rates of fluorine: 7.5 mole percent F (N diluent at cc./min. for 30 minutes followed by 15 mole percent F at 50 cc./min. for two hours. Total F passed through the reactor is approximately 25 mmoles.

The volatile products contained in a liquid oxygen trap are fractionated through traps cooled at -78 C., l19 C., and 196 C. using vacuum line techniques. The majority of the products are found in the 196 C. fraction (2.25 mmoles). The -119 C. fraction contains 0.35 mmole and the -78 C. fraction contains only 0.02 mmole.

The -196 C. fraction (pale yellow in solid phase) and the 119 C. fraction (yellow in solid and liquid phase) are subjected to gas chromatography to separate CF Ol(CF CO shows the following absorptions: 7.08(w.), 7.63 (m.), 8.05(s.), 8.23(s.), 8.70(m.), 9.54(m.), 9.90(W.), 11.13 (m.), 1l.65(m.), 13.17(W.), 8.I1d 14.08(W.) microns. The mass spectrum of CF Cl(CF )CO also is consistent with the assigned structure.

The fluorination of the monolithium salt of chloropentafluoro-2,2-propanediol (see above) also yields the chlorodifluoromethyltrifluoromethyldioxirane. The fluorination conditions are similar to those for the disalt.

What is claimed is:

1. A compound of the formula R O R wherein R is fluorine or completely halo-substituted alkyl of not more than 9 carbon atoms, said halo being limited to fluorine only, or at most, one chlorine atom replacing a fluorine atom and the compound contains not more than 10 carbon atoms, at least one R being other than fluorine.

2. A compound according to claim 1 wherein each R is a completely halo-substituted methyl.

3. Perfluorodimethyldioxirane.

4. Chlorodifluoromethyltrifluoromethyldioxirane.

5. The process of preparing a compound of the formula wherein R is fluorine or completely halo-substituted alkyl of not more than 9 carbon atoms, said halo being limited to fluorine only, or at most, one chlorine atom replacing a fluorine atom and the compound contains not more than 10 carbon atoms, at least one R being other than fluorine, which comprises directly fluorinating with elemental fluorine at a temperautre of from about 100 to C. a compound having 2 oxygen atoms bonded to the same carbon atom to effect ring closure to form the 3-membered ring containing the peroxide group.

References Cited UNITED STATES PATENTS 2,570,435 10/1951 Downing et a1. 260648 2,871,260 1/1959 Drysdale 260648 3,030,408 3/1962 Inman et a1. 260-694 3,149,126 9/1964 Milas 260338 ALEX MAZEL, Primary Examiner I. H. TURNI-PSEED, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Page 1 Patent No. 3,632,606 Dated January 4, 1972 Inventor(s) Richard L. Talbott and Phillip G. Thompson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Column 2, Table I, let formula in 3rd vset M/n M/n 0 should be O II I II I c c cl/ Column 2, Table I, let formula. in -Ith set I v OH o OH 0 should be a L Column 2, Table I, 2nd formula in Ith set O OO should be -C- C -C- C- Column 5, 1st column, 3rd formula 7 CF CF CF C 3CH CCF CF CH 7 should be CF CF CF CCH CCF CF CF FORM PO-IO (10-69) USCOMM-DC 60376-P69 A U.S. GOVERNMENT PRINTING OFFICE I959 0-366-334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Page 2 Patent No. 3,632,606 Dated January a, 1972 Inventor(s) Richard L. Talbott and Phillip G. Thompson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

line 3l-formula Column 13,

CF CF CFCF Should be CF CF CFCF (3F (IF NO N02 Column 16, line 20, "825" should be -8.25-

. FORM PO-IOSO (10-69) Column 16, line 62, "(N diluent should be "(N2 diluent)-- Signed and seeld this 18th day of July 1972.

(SEAL) Attest:

ROBERT GO'ITSCHALK EDWARD M.FLETCHER,JR Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 u.s, GOVERNMENT PRINTING OFFICE: 1969 0-366-334 

